Oozeer R, Goupil-Feuillerat N, Alpert C A, van de Guchte M, Anba J, Mengaud J, Corthier G
Unité d'Ecologie et de Physiologie du Système digestif. Unité de Génétique Microbienne, INRA, 78350 Jouy en Josas, France.
Appl Environ Microbiol. 2002 Jul;68(7):3570-4. doi: 10.1128/AEM.68.7.3570-3574.2002.
Live Lactobacillus casei is present in fermented dairy products and has beneficial properties for human health. In the human digestive tract, the resident flora generally prevents the establishment of ingested lactic acid bacteria, the presence of which is therefore transient. The aim of this work was to determine if L. casei DN-114 001 survives during transit and how this bacterium behaves in the digestive environment. We used the human flora-associated (HFA) mouse model. L. casei DN-114 001 was genetically modified by the introduction of erm and lux genes, encoding erythromycin resistance and luciferase, respectively. For this modified strain (DN-240 041), light emission related to luciferase expression could easily be detected in the contents of the digestive tract. When inoculated into the digestive tract of HFA mice, L. casei (DN-240 041) survives but is eliminated with the same kinetics as an inert transit marker, indicating that it does not establish itself. In pure culture of L. casei, luciferase activities were high in the exponential and early stationary growth phases but decreased to become undetectable 1 day after inoculation. Viability was only slightly reduced even after more than 5 days. After transit in HFA mice, luciferase activity was detected even when 5-day-old L. casei cultures were given to the mice. In culture, the luciferase activity could be restored after 0.5 to 7 h of incubation in fresh medium or milk containing glucose, unless protein synthesis was inhibited by the addition of chloramphenicol or rifampin. These results suggest that in HFA mice L. casei DN-240 041, and thus probably L. casei DN-114 001, is able to initiate new protein synthesis during its transit with the diet. The beneficial properties of L. casei-fermented milk for human health might be related to this protein synthesis in the digestive tract.
活的干酪乳杆菌存在于发酵乳制品中，对人体健康有益。在人体消化道中，常驻菌群通常会阻止摄入的乳酸菌定植，因此乳酸菌的存在是短暂的。这项研究的目的是确定干酪乳杆菌DN-114 001在肠道转运过程中是否存活，以及该菌在消化环境中的行为表现。我们使用了人源菌群相关（HFA）小鼠模型。通过分别导入编码红霉素抗性的erm基因和荧光素酶的lux基因，对干酪乳杆菌DN-114 001进行基因改造。对于这种改造后的菌株（DN-240 041），在消化道内容物中能够很容易地检测到与荧光素酶表达相关的发光现象。当接种到HFA小鼠的消化道中时，干酪乳杆菌（DN-240 041）能够存活，但会以与惰性转运标记物相同的动力学被清除，这表明它无法定植。在干酪乳杆菌的纯培养物中，荧光素酶活性在指数生长期和早期稳定期较高，但在接种后1天就会下降至无法检测到。即使在5天多之后，存活率也只是略有降低。在HFA小鼠体内转运后，即使给小鼠投喂5日龄的干酪乳杆菌培养物，仍能检测到荧光素酶活性。在培养过程中，除非添加氯霉素或利福平抑制蛋白质合成，否则在含有葡萄糖的新鲜培养基或牛奶中孵育0.5至7小时后，荧光素酶活性可以恢复。这些结果表明，在HFA小鼠中，干酪乳杆菌DN-240 041，因此可能还有干酪乳杆菌DN-114 001，在随食物转运过程中能够启动新的蛋白质合成。干酪乳杆菌发酵乳对人体健康的有益特性可能与消化道中的这种蛋白质合成有关。
